Nicoletti assay The Nicoletti assay, named after its inventor, the Italian physician Ildo Nicoletti, is a modified form of cell cycle analysis. It is used to detect and quantify apoptosis, a form of programmed cell death, by analysing cells with a DNA content less than 2n ("sub-G0/G1 cells"). Such cells are usually the result of apoptotic DNA fragmentation: during apoptosis, the DNA is degraded by cellular endonucleases. Therefore, nuclei of apoptotic cells contain less DNA than nuclei of healthy G0/G1 cells, resulting in a sub-G0/G1 peak in the fluorescence histogram that can be used to determine the relative amount of apoptotic cells in a sample. This method was developed and first described in 1991 by Nicoletti and co-workers at Perugia University School of Medicine. An optimised protocol developed by two of the authors of the original publication was published in 2006. The objects measured within the sub-G0/G1 peak, with DNA content lesser than 5% of that of the G0G1 peak, in all probability are apoptotic bodies and thus do not represent individual apoptotic cells References Further reading Biological techniques and tools Cell biology Cell cycle Flow cytometry